Manufacture of lithium hydroxy carboxylic acid soap greases



2,697,693 Patented Dec. 21, 1954 MANUFACTURE OF LITHIUM HYDROXY CAR- BOXYLIC ACID SOAP GREASES George V. Browning, Schenectady, N. Y., Lawrence C. Brunstrum, Flossmoor, 111., and Wilbur L. Hayne, Jr., Hammond, Ind., assignors to Standard Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Application November 5, 1951, Serial No. 254,986

15 Claims. (Cl. 252-41) The present invention relates to improvements in the manufacture of lithium soap greases. More particularly, it relates to improvements in the manufacture of greases comprising lithium 12-hydroxy stearate or the lithium soap of hydrogenated castor oil and a lubricant base such as a mineral lubricating oil or the like.

Lithium IZ-hydroxy stearate greases are ordinarily prepared commercially by heating a mixture of the soap and oil to above about 400 F., e. g. 425 F., in order to melt the soap and obtain a high degree of dispersion of soap in oil following which the mix is cooled from the melting temperature and milled either during the cooling or thereafter, if for example, shock chilling is employed. Heating the soap-oil mixture to such a temperature incurs certain difliculties, particularly when the grease is intended for use at very low temperatures at which the oleaginous vehicle, e. g. a mineral oil, must of necessity be of low viscosity and relatively high volatility. Equipment requirements pose a problem when operating at such temperatures because it is necessary to employ special heat exchange equipment, safety devices to guard against the fire hazard which is present with volatile oils, etc. Such high temperatures likewise have a deleterious effect on the oxidation stability of the greases. The prior art, of course, does suggest methods for the manufacture of lithium hydroxy stearate greases at temperatures below the melting point of the soap but these have generally been unsatisfactory in various respects. Such greases have had low yields (i. e. high soap contents), poor worked and unworked consistency and usually have not been mechanically stable. It is an object of the present invention to provide an improved method of, preparing lubricant greases comprising lithium soaps of long chain hydroxy fatty acids. A further object of the present invention is to provide an improved low temperature process for the manufacture of semi-solid to solid lubricant greases comprising lithium 12-hydroxy stearate or the lithium soap of hydrogenated castor oil.

Another object of the invention is to provide a method of preparing superior yields of such lithium soap greases at steam kettle temperatures. A still further object of the present invention is to provide a method for the manufacture of lithium 12-hydroxy stearate greases and the like whereby uniformity of product from one batch to another can be consistently obtained. Another object is to provide a method of preparing semi-solid to solid greases of high consistency which are suitable for low temperature use. These and additional objects and advantages will be apparent from the following description of our invention.

In a preferred embodiment of the present invention a lubricant grease is prepared by charging a mixture of 12-hydroxy stearic acid, lithium hydroxide hydrate, water, and an oleaginous vehicle, preferably a solvent extracted mineral oil, to a jacketed pressure vessel having a stirring mechanism therein. After having charged the vessel with the above named constituents, the vessel is sealed and the contents are heated by introducing steam to the- 2 pounds per square inch. The mixture within the vessel is continuously agitated while it is being heated in this manner. When the temperature of the batch reaches the desired point it is preferably held at such temperature for a relatively short time, c. g. from about 10 minutes to about an hour or longer, after which the steam is vented in order to relieve the pressure. The venting of steam may be begun the moment the temperature reaches the desired level but as a practical matter it is desirable to hold the batch at such temperature for a short period of time. It is critical, when venting the steam, that the temperature of the batch be held at substantially the same temperature to which it had been heated, i. e. there should be no more than about 10 drop in batch temperature during the removal of steam. Rapid agitatlon should be continued during the release of steam. The introduction of steam to the vessel jacket at somewhat higher pressure results in the heat necessary to drive off the steam without causing a drop in the temperature of the batch itself. When the steam is flashed from the vessel without regard to reduction in temperature of the batch, although a somewhat improved product is obtained as compared to merely heating the mixture to such a temperature at atmospheric pressure, a softer grease having much poorer consistency results. When the vessel is opened, after the pressure is relieved, the contents often appear lumpy and somewhat grainy but can readily be smoothed to the desired consistency by milling the same, e. g. in a colloid mill. The resulting grease possesses excellent mechanical and oxidation stability and low leakage characteristics.

By the term yield as employed herein is meant the relationship between the amount of soap employed and the amount of oleaginous vehicle employed to produce a given quantity of grease of desired properties. Thus, the smaller the amount of soap employed to obtain a given quantity of grease of a particular consistency, the higher is said to be the yield.

The yields of grease which are obtainable by the present method are a substantial improvement over those obtained by prior art methods employing temperatures below the melting point of lithium l2-hydroxy stearate or the lithium soap of hydrogenated castor oil. Thus, by our novel process, greases having excellent penetration values and fiber dispersement are obtainable with soap contents as low as about 3 to about 15 per cent. When oil and such relatively low amounts of soap constituents are heated to the temperatures employed in accordance herewith in an open kettle (without pressure) a fluid slurry, rather than a grease, results. Higher percentages of soap, for example 15 to 30 per cent or even more, may of course be employed if desired. Greases prepared in accordance with the present invention have been found to be equivalent in every way, if not superior, to greases prepared by high temperature prior art methods.

In accordance with the present invention, it is essential that the batch, before heating, constitute at least about 1 per cent of water by weight, preferably at least about 1% per cent. Larger amounts of water may be employed, but more than about 5 per cent appears to be unnecessary since it does not contribute to any substantial improvement but must nevertheless be vented without reiducing batch temperature which obviously would be a waste of heat. The continued presence of water in such an amount during the heating step contributes, in large measure, to achievement of the various objects of the invention.

The method of the present invention is described with particular reference to lithium soap prepared from 12- hydroxy stearic acid but it should be understood that lithium soap of hydrogenated castor oil may be employed with equally advantageous results. The soap constituents of the grease may, if desired, comprise part lithium 12- hydroxy stearate and part the lithium soap of hydrogenated castor oil. Acyclic acids containing 12 or more carbon atoms and one or more hydroxyl groups separated from the carboxyl group by at least 1 carbon atom mtg be advantageously employed in accordance herew1 Oleaginous vehicles which may be employed in accordance herewith are for example mineral oils in the lubricating oil viscosity range, i. e. about 80 S. S. U. at 100 F.. to about. 300 .S. S., U.,. at. .7210" F., preferably salvent extractedloils in said'rang'e, i. oils fromwhich' a sub-1 I t lsupl as .by extraction with, phenol, furfural, B,1}f -die hloroclr ethylether. (Chlorex), liquid S02, nitrobenzene, etc are stantial portion of the aromatics have been re particularly desirableand preferredfor use in accord?" Synthetic lubricat ng ance;with the. present invention.

oils. resulting. frompolymerizatlon of unsaturated hy drocarbonslor. otherfloleaginous compounds within the lubricating. oil viscosity ,range such asthe highlmole'cu lar' weightethers. e. g.,,normal hexylethen etc. may be employed..-? .Because. of thetQmperaturesemployed the res of .low tern- Whereas the present inventlon offers a particularly ad'- vantag'eous methodwhereby all of the desired constituents may. be added at thev outset, it is not necessary to 'charge the total, amount of the oleaginous vehicle to the-pressure vessel initially. Thus, it may be desirable to charge the soapeonstituents, water, and a relatively small percentage of theamount of vehicle ultimately employed in order to make optimum'use' of available autoclave capacity and produce a large batch of high soap content material which may then. be-mixed.hot,with the rest of the oleagino us vehicle and imilledto, give the relatively low-soap content finaliproducth 1.

:The preferred embodiment of the present invention has be'endescribed with reference to the addition of lithium hydroxide-monohydrate andj l2- hydroxy stearic acid' to the reaction vvessel .withth'e formation of the soap taking place' in s'itu; it should be understood that thejsoap may beprepared outside of the vessel and charged'thereto in the desired amount without departing .from the spirit of the presentinvention. As a practical matter it is usually more expedient to prepare the soap in situ and eliminate the separate soap making step. Furthermore, although lithium hydroxide-'monohydrate is taught as the preferred neutralizing agent, .the anhydrous lithium hydroxide may likewise. be employed. Inasmuch as greases may be produced in' accordance herewith by starting with either'a previously prepared soap, e. g. lithium 12-hydroxystearate; etc'., or 'by using the soap reactants and saponifying in situ during the preparation of the grease, the termlithium hydroxy soap constituents as employed in the appended claims shall include both a previously prepared soap and the reactants which upon being subjected to the process of the present invention will saponifyin situ to produce such a soap. V, .--'The pressure within the vessel increases'as the temperature is increased by "introduction of a heat -exchange medium such as high pressure steam to .theivesseljacket'. One'of the particularladvanta'ges of this inv'entionristhat such excellent yields of grease may-be prepared athigh pressure steam temperatures butotherheating' mediums may be employed. The pressurewithin thevessel' itself'is ordinarily atjsomelpointbelow thepre'ssureof the steam employed as heating'medium. Greases may ."be prepared in accordance herewith at temperatures'as low as about 275'IF. It is preferredjhowever, 'to operate at'a temperature' of from about 3005B to about 330F'. A gradu'akincre'asedn"yield and overall 'imp'rovenrent"in grease properties are observed for products 'pro'ducedat temperatures-up to about 340 F. but little .if any improvement has been observed when operating at 'a temperature thereabove I The following operating examples'are included eifically'-illustrate the present invention without the 'm'tent'ion ef unnecessarily lim'iting the same; T-lie tests" set forth'iii these examples were-carried out in a mechanically stirred, jacketed autoclave having a capacity of 210 gallons l. tr x; .ft') 1.. H 'EXAMPLE 1" It I.

tSQO pounds of a mixture, comprising 89.6 per nto'f'a pnei rex; "acted. Q lubricating oil," glsprcen izhydroxvf stea'ric acid, 1, percent flithiu'rr'i hydroxide monohydrateand .2 percent of an" an'iine type oxidation inhibitor marketed by DuPont under the designation PSF- oi 'Ortholeum. 300 (a mixture of siibstitutedl'arbmatic airilnes), wasehar'ged to theaut'ocla'vel "To"thismixtiife was added 30 pounds of Water and the autoclave was sealed. By introducing high pressure steam to the j of the autoclave the mixture -'was then heated with agitation to 300 F. at which temperature an internal pressure of 75 pounds per square inch-was'developed. The batch was held at 330 F. for about minutes after which the steam was'v'entedrapidlv with a substantial 'drop'in batch temperature. "A-f'r'elatively soft grease having an unworked penetration at 77 of 337 and a worked penetration of 3 42 was-obtained by milling a'sample of.the batch in' "a-'colloid-mill -Electron photomicrographs of the sample indicate relatively-poor dispersion of soap fibers and a poor L/ D ratio.

2 -.-EXAMP.LE 2

The batch prepared 'inExar'nple l, was reheated to a temperature of 330 F. in the autoclave after having added 25 pounds of' water'thereto. A pressure of 75 pounds per square inch-was developed in the autoclave. The batch was held at such temperature for approximately 30'minutes. The pressure was then relieved by venting the steam while being careful to maintain the batch temperature at -330- F.- by the-introduction of additional amounts of high pressure steam-to. the jacket and stirring the-mix-at full speed. A heavier more fibrous product was obtained which upon removing a sample and milling it in a colloid mill gave a smooth grease having an unworked; penetrationof 276 and a worked penetration of 278. The'dropping point of this grease was 390 F. and electron photomicrographs indicated that the fibers were well dispersed with a good L/ D ratio.

. v 5,.1 X/'. -L ..'The same batch which had'been initially prepared in accordance withthe method set forth in Example 1 and then reheated inaccordance with-the method set forthin Example 2'was reheated for a third time-after having added -25- pounds of water-thereto. After holding the mix at a-temperatureof 330 F. and 75 pounds per square inch for-a short time the valve was opened and the pressure was relieved rapidly (-over-a.period of 5 to 10-minutes )--withoutregardtbmairitaining tlieternperature of the batch at 330? A'sharp'dr0p of about 25 F. inthe temperature ofthe batch occurred. A=sample of the resulting product'was milled'in a colloid-mill to give a somewhat softer product having an; unworked penetration of 294-- and-a worked penetration -of*293. Electron photomicrographs of this grease indicate poorer dispersion of soap fibers than than preparedain accordance with Example 2. I a

1. l g1. E M LE A *1 he batch" from Example 3'was reheated to a temperature of 33'0-F. and-a pressure of about-75 pounds per square-inchzafter adding '25 pounds-of water." Thebatch was maintained under those-conditions for 3 hours after which the pressure was relieved slowlywhile agitating the batch "rapidly with no, temperature drop. A- sample of the batch -was-:then milled and a grease having an unworked penetration-of" 265 and a worked penetration-of 266 was obtained; Electron photomicrographs of. this grease indicated no large fibers and slightly better dispersion than that obtained in any of the first three examples. XAMBLE ."f --Another grease prepared in'accordance with the method of Example :1 was-heated with -25 pounds of water :but this time a pressure of only 30 to 39 pounds per square inch and'a top temperature Jof'ab'out 275 F. was reached. After holding the batch at such temperature for 3 /2 hours -the=- pressure was vente'd off without loss of temperature and after milling a sample; thereof resulted in a grease having an unworked penetration somewhat over 400. p 1.1 .1. i I. l P

'l'he ba'tch from Example 5 was reheated withan-added '2 5 pounds'of water to 'a temperat'ure-of 320 F. and a pressure of topounds per square inch and held at such temperature and pressure forlhour. Thepressure excellent appearance. L The unworked penetration of .the

grease waslfi t'anti' after 60 strokes it was 274. Electron photomicrographs indicate excellent dispersion of soap fibers and good L/D ratio.

EXAMPLE 7 EXAMPLE 8 The batch of Example 7 was again heated'with 25 pounds of water to a temperature of 335 F. and a pressure of 90 pounds per square inch. The pressure was slowly relieved without loss in batch temperature and a grease was obtained after milling a sample of this material which had an unworked penetration of 254 and a worked penetration of 278.

EXAMPLE 9 pounds of water were added to the batch from Example 8 and the mixture was heated to a temperature of 335 F. and a pressure of 90 pounds per square inch. The high pressure steam was then shut off and water was introduced to the jacket of the autoclave to condense the steam within the vessel. After the pressure was completely reduced the vessel was opened and the water was boiled off. A sample was removed, milled and tested for consistency. An unworked penetration of 339 and a worked penetration of 354 was obtained. Electron photomicrographs indicate considerable break down and lack of continuity between fibers.

EXAMPLE 10 600 pounds of a mix comprising 88.6 percent of a phenol-extracted SAE 40 lubricating oil, 10.2 percent of hydrogenated castor oil, 1.6 percent of lithium hydroxide monohydrate (LiOH.HzO), 0.2 percent of an amine type oxidation inhibitor marketed by DuPont under the designation PSF-34, and pounds of water were charged to the autoclave. The temperature of the batch was raised to 320 F. and a pressure of 68 pounds per square inch was developed in the vessel. After venting the pressure without loss in batch temperature a sample was removed and milled in the colloid mill to give an unworked penetration of 262 and a worked penetration of 260. The penetration of the grease at 500 strokes was 260 and at 95,000 it was 286. The dropping point was 388 F. and electron photomicrographs indicate excellent dispersion and L/D ratio. Negligible leakage was encountered in tests on this grease.

EXAMPLE 1 1 405.7 pounds of a mix comprising 9.7 percent 12- hydroxy stearic acid 1.6 percent lithium hydroxide hydrate and the remainder phenol extracted SAE 40 lubricating oil was heated to 300 F without sealing the autoclave, and was maintained at that temperature for about minutes. A slurry resulted which comprised 10.5 percent soap.

To the slurry of Example 11, which obviously was unsatisfactory as a grease were added varying amounts of water (as set forth in Table I) and the batch was heated after each addition to 300 F. under pressure. The pressure was vented without loss in batch temperature, a sample was taken and tested for consistency and then the next larger amount of water was added, heated, etc. Thus, as may readily be seen from the following table, the use of pressure technique in accordance with the present invention with even slight amounts of water greatly improves the yield of grease. In accordance with the present invention, therefore, at least about 1 percent water by weight should be added to the mix, and preferably at least about 1 /2 to about 2 percent water. As indicated hereinabove, considerably more water may be used without departing from the spirit of the present invention but more than about 5 percent does not give an apparent improvement and merely makes it necessary to vent the additional amounts of steam before the milling operation can begin.

Table l H2O (p gigi gggt f' *By weight based on total mix. "Unworked penetration.

EXAMPLE 12 400 pounds of a mix consisting of phenol extraeted SAE 40 lubricating oil and sufficient 12-hydroxy stearic acid and lithium hydroxide monohydrate to give 7 /2 percent soap concentration was prepared by heating the.

mix with 12 pounds of water to a temperature of 300 F. at which a pressure of 70 pounds per square inch was developed. The batch was held at this temperature for a short time and the steam was then vented without loss in temperature. The vessel was opened after the pressure was released while maintaining .the batch at 300 F. and 0.1 percent of an amine type oxidation inhibitor marketed by DuPont under the designation PSF-34 or Ortholeum 300 (a mixture of substituted aromatic amines), was added thereto. The A. S. T. M.

.oxidation test was then conducted on a sample of the batch which has been milled in a colloid mill. In this test a 5 pound per square inch drop in oxygen pressure in hours is considered failure for most greases. Set forth below are the results of this test.

Although the present invention has been described with particular reference to batch operation it is not limited thereto and may be carried out continuously or semi continuously in known commercial equipment. A simple expedient which is particularly economical and yet highly advantageous is to employ two or more autoclaves and one or more colloid mills so that a batch may be milled while another batch is being heated, etc. i

Various antioxidants, other than the product set forth in the above examples, may of course be used. A particularly desirable antioxidant is phenyl alpha-naphthylamine which may be added in proportions of about 0.01 to about 1 per cent by weight, based upon the finished grease. In addition we may add fillers such as talc or asbestos, solid lubricants, such as graphite, dyes, odorant materials, metal deactivators, corrosion inhibiting compounds, etc.

The pressures given hereinabove and in the appended claims are gauge pressures. Percentages given are by weight unless otherwise specified.

The greases prepared in accordance with the present invention are of the anhydrous type hence it should be understood that essentially all of the water is removed as steam during the venting operation. Obviously the moisture content of the grease could be readily adjusted to any level if for any reason it were found desirable to have a certain amount of water in the finished product.

While we have described our invention with particular reference to certain preferred embodiments thereof, it is to be understood that these are by way of illustration and not by way of limitation.

We claim:

1. A method of producing a grease comprising a lubricant base and a lithium soap of an organic acid substance selected from the group consisting of hydrogenated castor oil and hydroxy fatty acids of at least 12 carbon atoms wherein the hydroxyl group is separated from the carboxyl group by at least one carbon atom, which method comprises subjecting a mixture comprising lubricant base, lithium hydroxy soap constituents and at least about 1 percent of water to a temperature of at least about 275 F. and superatmospheric pressure, agitating said mixture, relieving the pressure after the J t F; mixturehas reached said temperature by venting the steam therefrom, and maintaining said mixture at substantially'said 'temperature while ventingsaid steam.

2. The method of claim 1 wherein the lubricant base is a solvent extracted petroleum oil in the lubricating oil VlSCOSllIy range:

'3; A method of producing'a grease comprising a lubricant base and "a lithium soap vof. a. hydroxyiatty acid having at least 12 carbon atoms wherein the hydroxylgroup is separated fromthe carboxyl group by at least one"carbonatomwhich-method comprises subjecting a mixture comprising lubricant base; lithium hydroxy soap constituents and at least about 1 percent of water to a temperature in the range of at'sleastabout 275 F. and superatmosphericv pressure, .agitating said mixture,- Iclieving the pressure temperature bj 'ventingthefsteam therefrom, maintaining said. mixture atzsubs'tantially said temperature while venting 'sai'd steamhand .millingthe resulting product, p

4. The=method of claim wherein the lubricantbase is a: solyentextracted petroleum oil in the lubricating oil viscosity.range.l. v H

5; The method claim 3Lwherein the mixture is sub-' jeeted to a temperature in the -range of from. about 300, F.to abouta340fnFr and water is..present in amount of about i /2 percenttoaboutj percents 1 L 6. The-method .of-.claim 3- hcrein the l lithium 'hy droxy; s'oap' constituents comprise an amount of ,from about 3'percent to about 30 percent of the mixture "7 The method of claim 3 wherein thelithium hydroxy soap constituents Icomprise lithium lZ-hydroxy stearate. 8. A method of'producing a greasecomprising a lubricant base and 'a lithium soap of awhydrogenated ,castor oil which method'comprises subjecting a mixture com p'ri'sing' lubricant ba'se, lithium hydrogenated castor, oil.

soap constituents and-atleast about 1 percent of water to =atemperature-of at-least about 275 WF. and superatmospheric pressure, agitating said .mixture, relieving the pressure afterthe mixture has reached said temperature by-venting the steam therefrom, maintaining said -mixture' at substantially said .temperature while venting said steam andmilling .theresulting :product. q, 9.- Thermethod vof claim 8' wherein the lubricantbasc comprises a solventextracted petroleum oil in the lubrieating oil viscosity range... f s.

10+ The method of. claim 8.wherein,sthe mixture is sub jected to a Itemp'er'aturein the rangeof. from about 300 F. to about 34051 and 'water is present in an amount of about 1% percent to about percent.

afterL-Jthe mixture has reached said.

l the mixture.-

-, solvent extfactedpetroleumioilllubricaiitbase a:

and milling' the resulting product.

11. The method of h15i5hs"whieih the lithium hy rose atedr 9 ..-Qi q phcpg it m s-- ntj e.. a amountpf from about 3 percent toabout' percent of genated easter oil soap-constituents soap of hydrogenated qa s't oipil."

comprises subjecting a mixture comprising 'lubricantb'ase,

lithium hydro'gnatedcastor oil soap constituents and at least about it percent of water to a. temperature. th'e': range of from about 3'00 F. to about 340 F. and'a'pres sure of at least about 5 0'pounds per square inch',agita'ting said mixture,*relieving tlie pressure after the mixture has reached said temperatureby venting'the ste'am there'- from,m" intaimn'gsaid' mixture at substantially said'temperature while venting'said steam and milling the resultingproduct. l5.'The methodof claim 14wl1'1chinclude's the step of adding an antioxidant to said mixture.

References Cited intlie file of this patent STATES PATENTS Number. 72 Date :APT- 2,417,495-

Mar'; 1.8, 1195? 2 41 53 l in- 13119543 2,444,720 July 6, 19,423: 2,450,219 Sept. 23,- 1943' 2,450,220 H Sept. 2 1948 2,450,254 shram et aI sea 28;, 19 48: 2,450,255 Ashburr'i et a1. Sept, 28, 124a 2,483,282 Houlton Sept. 27, 1949 

1. A METHOD OF PRODUCING A GREASE COMPRISING A LUBRICANT BASE AND A LITHIUM SOAP OF AN ORGANIC ACID SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYDROGENATED CASTOR OIL AND HYDROXY FATTY ACIDS OF AT LEAST 12 CARBON ATOMS WHEREIN THE HYDROXYL GROUP IS SEPARATED FROM THE CARBOXYL GROUP BY AT LEAST ONE CARBON ATOM, WHICH METHOD COMPRISES SUBJECTING A MIXTURE COMPRISING LUBRICANT BASE, LITHIUM HYDROXY SOAP CONSTITUENTS AND AT LEAST ABOUT 1 PERCENT OF WATER TO A TEMPERATURE OF AT LEAST ABOUT 275* F. AND SUPERATMOSPHERIC PRESSURE, AGITATING SAID MIXTURE, RELIEVING THE PRESSURE AFTER THE MIXTURE HAS REACHED SAID TEMPERATURE BY VENTING THE STEAM THEREFROM, AND MAINTAINING SAID MIXTURE AT SUBSTANTIALLY SAID TEMPERATURE WHILE VENTING SAID STEAM. 